Light-emitting elements, in which nitride semiconductors are used, can emit light from near ultraviolet to red regions by virtue of the wide bandgap properties thereof, and accordingly, a variety of research on these light-emitting elements has been conducted. The general structure of a nitride semiconductor light-emitting element includes a semiconductor laminated structure, in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are laminated on a substrate. Typically, an electrode is provided on approximately the entire surface of the p-type nitride semiconductor layer.
In some types of nitride semiconductor light-emitting elements, a light transmissive electrode made of a metal oxide, such as indium tin oxide (ITO), is employed as the electrode that is provided on approximately the entire surface of the p-type nitride semiconductor layer, and light is emitted through the light transmissive electrode: The light transmissive electrodes made of ITO and the like have high resistivity compared with metal electrodes, such that the light transmissive electrodes must be increased in thickness to obtain sufficient current diffusibility. However, an increase in the thickness of the light transmissive electrodes may lead to an increase in the light absorbed by the light transmissive electrodes. In order to solve the aforementioned problems, Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2006-156590) discloses that a current diffusion layer made of metallic materials is further provided between the p-type nitride semiconductor layer and the light transmissive electrodes so as to compensate for the current diffusibility of the light transmissive electrodes, thereby reducing the thickness of the light transmissive electrodes.
However, while the amount is small, absorption of light occurs in a light transmissive electrode made of a metal oxide such, as ITO. Accordingly, a further increase in the light output of the semiconductor light-emitting element and the suppression of the absorption of light by the electrodes is desired.
It is an object of certain embodiments of the present invention to provide a semiconductor light-emitting element that suppresses the absorption of light by an electrode and realizes a further increase in optical output.